Messages in this thread | | | Subject | Re: [PATCH 1/3] mm,memory_hotplug: export mhp min alignment | From | Max Gurtovoy <> | Date | Thu, 3 Jun 2021 13:52:59 +0300 |
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On 6/2/2021 3:14 PM, David Hildenbrand wrote: > On 02.06.21 13:10, Max Gurtovoy wrote: >> Hotplugged memory has alignmet restrictions. E.g, it disallows all >> operations smaller than a sub-section and only allow operations smaller >> than a section for SPARSEMEM_VMEMMAP. Export the alignment restrictions >> for mhp users. >> >> Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com> >> --- >> include/linux/memory_hotplug.h | 5 +++++ >> mm/memory_hotplug.c | 33 +++++++++++++++++++-------------- >> 2 files changed, 24 insertions(+), 14 deletions(-) >> >> diff --git a/include/linux/memory_hotplug.h >> b/include/linux/memory_hotplug.h >> index 28f32fd00fe9..c55a9049b11e 100644 >> --- a/include/linux/memory_hotplug.h >> +++ b/include/linux/memory_hotplug.h >> @@ -76,6 +76,7 @@ struct mhp_params { >> bool mhp_range_allowed(u64 start, u64 size, bool need_mapping); >> struct range mhp_get_pluggable_range(bool need_mapping); >> +unsigned long mhp_get_min_align(void); >> /* >> * Zone resizing functions >> @@ -248,6 +249,10 @@ void mem_hotplug_done(void); >> ___page; \ >> }) >> +static inline unsigned long mhp_get_min_align(void) >> +{ >> + return 0; >> +} >> static inline unsigned zone_span_seqbegin(struct zone *zone) >> { >> return 0; >> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c >> index 9e86e9ee0a10..161bb6704a9b 100644 >> --- a/mm/memory_hotplug.c >> +++ b/mm/memory_hotplug.c >> @@ -270,24 +270,29 @@ void __init >> register_page_bootmem_info_node(struct pglist_data *pgdat) >> } >> #endif /* CONFIG_HAVE_BOOTMEM_INFO_NODE */ >> +/* >> + * Disallow all operations smaller than a sub-section and only >> + * allow operations smaller than a section for >> + * SPARSEMEM_VMEMMAP. Note that check_hotplug_memory_range() >> + * enforces a larger memory_block_size_bytes() granularity for >> + * memory that will be marked online, so this check should only >> + * fire for direct arch_{add,remove}_memory() users outside of >> + * add_memory_resource(). >> + */ >> +unsigned long mhp_get_min_align(void) >> +{ >> + if (IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP)) >> + return PAGES_PER_SUBSECTION; >> + return PAGES_PER_SECTION; >> +} >> +EXPORT_SYMBOL_GPL(mhp_get_min_align); > > We have to main interfaces to "hotplug" memory: > > a) add_memory() and friends for System RAM, which have memory block > alignment requirements. > > b) memremap_pages(), which has the alignemnt requirements you mention > here. > > I feel like what you need would better be exposed in mm/memremap.c, > for example, via "memremap_min_alignment" so it matches the > "memremap_pages" semantics. > > And then, memremap_pages() is only available with CONFIG_ZONE_DEVICE, > which depends on SPARSEMEM_VMEMMAP. So you'll always have > PAGES_PER_SUBSECTION. > > I can already spot "memremap_compat_align", maybe you can reuse that > or handle it accordingly in there?
Yes I think that since subsection is aligned to PAGE_SIZE I can do:
size_t pci_p2pdma_align_size(size_t size) { unsigned long min_align;
min_align = memremap_compat_align(); if (!IS_ALIGNED(size, min_align)) return ALIGN_DOWN(size, min_align);
return size; }
thoughts ?
>
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